Worth Regearing?

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kong24680

kong24680

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I currently have a Stage 2 Harrop supercharger (~500whp) on my 2021 LX570. I’m planning to add front and rear e-lockers soon and am considering whether regearing is worthwhile for running 37s. I’ve seen mixed opinions on whether regearing is necessary with the 8-speed transmission and supercharger setup. I’d love to hear your thoughts.
 
According to @TeCKis300 's post here:

forum.ih8mud.com

Definitive 200-series Gearing Reference

So I had a little time this morning to put together a chart combining transmission gearing of 6-speed vs 8-speed, diff ratios, and tire sizing into an overall gearing reference. Hoping this will be useful for those trying to understand how their changes are going to effect overall gearing of...
forum.ih8mud.com forum.ih8mud.com

I would say, yes, definitely re-gear. I would also say, do so with the diffs from a 3.9 (pre 2016 LX or landcruiser) and build your lockers on to those before installing. It will drive almost like stock with 37" tires.
 
CanadianRockyCruiser said:
According to @TeCKis300 's post here:

forum.ih8mud.com

Definitive 200-series Gearing Reference

So I had a little time this morning to put together a chart combining transmission gearing of 6-speed vs 8-speed, diff ratios, and tire sizing into an overall gearing reference. Hoping this will be useful for those trying to understand how their changes are going to effect overall gearing of...
forum.ih8mud.com forum.ih8mud.com

I would say, yes, definitely re-gear. I would also say, do so with the diffs from a 3.9 (pre 2016 LX or landcruiser) and build your lockers on to those before installing. It will drive almost like stock with 37" tires.
Click to expand...
What should I be regearing to? 4.3?
 
kong24680 said:
What should I be regearing to? 4.3?
Click to expand...
I think you should re-gear to 3.9 because it will get you almost exactly back to your factory ratios on 37" tires (as your stated goal).

I also expect that it may not be completely necessary to regear with the 8 speed and a stage 2 supercharger. However, if you're already in there for lockers, it seems to be the right time. Conveniently, you can pick up a used set of stock diffs from a pre 2016 (6 speed) LX or LC which are 3.9's, and build the e-lockers in that set. Then you can swap the built 3.9 diff's in without too much down time on the vehicle (most shops can do this in a day, hell, even I did mine in a day).
 
CanadianRockyCruiser said:
I think you should re-gear to 3.9 because it will get you almost exactly back to your factory ratios on 37" tires (as your stated goal).

I also expect that it may not be completely necessary to regear with the 8 speed and a stage 2 supercharger. However, if you're already in there for lockers, it seems to be the right time. Conveniently, you can pick up a used set of stock diffs from a pre 2016 (6 speed) LX or LC which are 3.9's, and build the e-lockers in that set. Then you can swap the built 3.9 diff's in without too much down time on the vehicle (most shops can do this in a day, hell, even I did mine in a day).
Click to expand...
I just found a local set of pre-2016 diffs that I’m planning on getting e-lockers put in with the stock 3.9 gearing. Appreciate the wisdom and guidance!
 
Here is my apples/oranges contribution:

I have a 6-speed and 35's, but I kind of regret re-gearing to 4.88. It's great off road and it engine brakes noticeably better. That's all good. In terms of peppy-ness for around town and highway driving, I did not find it a significant improvement at all. Different, yes, but not better or worse IMO. Cost to re-gear was minimal since I was putting in lockers anyway, but it was still a cost. And the gearing also prevents me from getting a more sensible tire size for snow tires, or if I decide to dial back to more road trips/towing/on-road type stuff if I ever change directions with my rig in the future.

Since you've got the 8-speed transmission and 3.3 axle ratios, I would suggest maybe 3.9 gears but don't go any deeper than that. The 8-speed is already pretty well sorted for larger tire diameters, and with the supercharger, you're not going to lacking for pep.

But ultimately, I think the best thing to do would be to hold of on the locker install and try it out with the big tires and supercharger for a while and see how you like it before deciding. Just my opinion.
 
+1 on a set of 3.90 Toyota gears. You’re wasting the supercharge if you’re on 37s as you’re nowhere near stock gearing.
 
Several factors in the trade space. I don't think it needs a re-gear with a S/C, but you may be forced into the regear anyways with 3. below.

  1. Gearing - the 8-speed doesn't need it. 37s with stock 8-speed gearing has a better overall ratio in first than 31s with the stock 6-speed gearing. 8th will be too tall generally on the freeway so using Sport S7 will keep the rig happier with less hunting.
  2. A supercharger will make for better off idle engine torque which again reduces the need for such low first gear
  3. If you're installing lockers on the 8-speed, IIRC, the 3.307 ring gear has a different thickness/carrier deck height that the locker may not be compatible with. This will require using a different ring gear anyways and the 3.9 is the answer, forcing the re-gear anyways. 3.9 is what you want. 4.1/4.3 are way too much gear for the 8-speed.
 
Thank you all for the guidance. Looks like I’m definitely going with the stock 3.9 gearing. Will provide feedback once everything is installed!
 
How has your experience been with the Harris supercharger?
 
Girl Dad of 3 said:
How has your experience been with the Harris supercharger?
Click to expand...
The truck has been at my shop the past 2 days getting tuned post install. I’m running a custom stage 2 setup with an 80mm pulley, 650cc injectors, 84mm Lexus RC-F, and snorkel on 91 octane, so my tuner (Yotawerx) is taking his time creating/fine tuning from scratch. Hoping to pick the car up tmw and plan to put some miles on it over the weekend.
 
kong24680 said:
The truck has been at my shop the past 2 days getting tuned post install. I’m running a custom stage 2 setup with an 80mm pulley, 650cc injectors, 84mm Lexus RC-F, and snorkel on 91 octane, so my tuner (Yotawerx) is taking his time creating/fine tuning from scratch. Hoping to pick the car up tmw and plan to put some miles on it over the weekend.
Click to expand...
Nice! Did you have Stage 1 previously, or going straight to stage 2?
 
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